Method for transmitting uplink data in a wireless communication system and device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for transmitting uplink data in a wireless communication system. According to an aspect of the present invention, the method comprising: receiving information including contention based channel configuration and traffic characteristic associated with the contention based channel configuration; configuring a contention based channel resource according to the contention based channel configuration; checking whether uplink (UL) data is suitable for the traffic characteristic associated with the contention based channel configuration; and transmitting the UL data using the contention based channel resource if the UL data is suitable for the traffic characteristic associated with the contention based channel configuration.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for transmitting uplink data.

BACKGROUND ART

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

DISCLOSURE Technical Problem

Based on the above-mentioned discussion, methods for transmitting uplinkdata in a wireless communication system and apparatuses therefor shallbe proposed in the following description.

Technical tasks obtainable from the present invention are non-limited bythe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a methodfor a user equipment (UE) operating in a wireless communication system,the method comprising: receiving information including contention basedchannel configuration and traffic characteristic associated with thecontention based channel configuration; configuring a contention basedchannel resource according to the contention based channelconfiguration; checking whether uplink (UL) data is suitable for thetraffic characteristic associated with the contention based channelconfiguration; and transmitting the UL data using the contention basedchannel resource if the UL data is suitable for the trafficcharacteristic associated with the contention based channelconfiguration.

In accordance with another aspect of the present invention, A UserEquipment (UE) for operating in a wireless communication system, the UEcomprising: a Radio Frequency (RF) module; and a processor operablycoupled with the RF module and configured to: receive informationincluding contention based channel configuration and trafficcharacteristic associated with the contention based channelconfiguration, configure a contention based channel resource accordingto the contention based channel configuration, check whether uplink (UL)data is suitable for the traffic characteristic associated with thecontention based channel configuration, and transmit the UL data usingthe contention based channel resource if the UL data is suitable for thetraffic characteristic associated with the contention based channelconfiguration.

Preferably, the contention based channel resource is a time-frequencyresource on which multiple UEs can transmit UL packet, simultaneously.

Preferably, the UL data is transmitted with an identifier of the UE onthe contention based channel resource.

Preferably, the information is received via a dedicated signaling orsystem information.

Preferably, the traffic characteristic includes at least one: a traffictype that can be transmitted by the contention based channel resource, amaximum packet size that can be transmitted by the contention basedchannel resource, a maximum delay that can be transmitted by thecontention based channel resource; a maximum error ratio that can betransmitted by the contention based channel resource; or a Quality ofservice Class Indicator (QCI) of traffic that can be transmitted by thecontention based channel resource.

Preferably, the information further includes an indication indicating atleast one radio resource control (RRC) state that can use the contentionbased channel resource.

Preferably, the information further includes an indication indicating atleast one radio resource control (RRC) state that can use the contentionbased channel resource.

Preferably, the contention based channel configuration includes at leastone: one or more radio resources of the contention based channelresource; subframe information of the contention based channel resource;Layer 2 configuration of the contention based channel resource; orsecurity information used for the contention based channel resource.

Preferably, if the UL data is not suitable for the trafficcharacteristic associated with the contention based channelconfiguration, the UE doesn't use the contention based channel resourceto transmit the UL data.

Preferably, the UE transmits the UL data using a UL grant received dueto scheduling request (SR) and buffer status report (BSR) if the UE isconnected and has a dedicated SR resource.

Preferably, the UE transmits the UL data using a UL grant received dueto random-access channel (RACH) and buffer status report (BSR) if the UEis connected but doesn't have a dedicated scheduling request (SR)resource, or the UE is in an idle state.

Preferably, if the information includes a multiple contention basedchannel configurations, a multiple contention based channel resourcesare configured according to the multiple contention based channelconfigurations, respectively.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

According to the present invention, the UE can reduce the datatransmission latency by using a contention based channel resource.

It will be appreciated by persons skilled in the art that that theeffects achieved by the present invention are not limited to what hasbeen particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2B is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3rd generationpartnership project (3GPP) radio access network standard;

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system;

FIG. 5 is a diagram for a general overview of the LTE protocolarchitecture for the downlink;

FIG. 6 is a diagram for Scheduling-request transmission;

FIG. 7 is a diagram for describing a random access procedure;

FIG. 8 is a flowchart illustrating data transmission according to anembodiment of the present invention;

FIG. 9 is a block diagram of a communication apparatus according to anembodiment of the present invention;

MODE FOR INVENTION

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition. In addition,although the embodiments of the present invention are described based ona frequency division duplex (FDD) scheme in the present specification,the embodiments of the present invention may be easily modified andapplied to a half-duplex FDD (H-FDD) scheme or a time division duplex(TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an Si interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of anInternet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation.

FIG. 5 is a diagram for a general overview of the LTE protocolarchitecture for the downlink.

A general overview of the LTE protocol architecture for the downlink isillustrated in FIG. 5. Furthermore, the LTE protocol structure relatedto uplink transmissions is similar to the downlink structure in FIG. 5,although there are differences with respect to transport formatselection and multi-antenna transmission.

Data to be transmitted in the downlink enters in the form of IP packetson one of the SAE bearers (501). Prior to transmission over the radiointerface, incoming IP packets are passed through multiple protocolentities, summarized below and described in more detail in the followingsections:

-   -   Packet Data Convergence Protocol (PDCP, 503) performs IP header        compression to reduce the number of bits necessary to transmit        over the radio interface. The header-compression mechanism is        based on ROHC, a standardized header-compression algorithm used        in WCDMA as well as several other mobile-communication        standards. PDCP (503) is also responsible for ciphering and        integrity protection of the transmitted data. At the receiver        side, the PDCP protocol performs the corresponding deciphering        and decompression operations. There is one PDCP entity per radio        bearer configured for a mobile terminal.    -   Radio Link Control (RLC, 505) is responsible for        segmentation/concatenation, retransmission handling, and        in-sequence delivery to higher layers. Unlike WCDMA, the RLC        protocol is located in the eNodeB since there is only a single        type of node in the LTE radio-access-network architecture. The        RLC (505) offers services to the PDCP (503) in the form of radio        bearers. There is one RLC entity per radio bearer configured for        a terminal.

There is one RLC entity per logical channel configured for a terminal,where each RLC entity is responsible for: i) segmentation,concatenation, and reassembly of RLC SDUs; ii) RLC retransmission; andiii) in-sequence delivery and duplicate detection for the correspondinglogical channel.

Other noteworthy features of the RLC are: (1) the handling of varyingPDU sizes; and (2) the possibility for close interaction between thehybrid-ARQ and RLC protocols. Finally, the fact that there is one RLCentity per logical channel and one hybrid-ARQ entity per componentcarrier implies that one RLC entity may interact with multiplehybrid-ARQ entities in the case of carrier aggregation.

The purpose of the segmentation and concatenation mechanism is togenerate RLC PDUs of appropriate size from the incoming RLC SDUs. Onepossibility would be to define a fixed PDU size, a size that wouldresult in a compromise. If the size were too large, it would not bepossible to support the lowest data rates. Also, excessive padding wouldbe required in some scenarios. A single small PDU size, however, wouldresult in a high overhead from the header included with each PDU. Toavoid these drawbacks, which is especially important given the verylarge dynamic range of data rates supported by LTE, the RLC PDU sizevaries dynamically.

In process of segmentation and concatenation of RLC SDUs into RLC PDUs,a header includes, among other fields, a sequence number, which is usedby the reordering and retransmission mechanisms. The reassembly functionat the receiver side performs the reverse operation to reassemble theSDUs from the received PDUs.

-   -   Medium Access Control (MAC, 507) handles hybrid-ARQ        retransmissions and uplink and downlink scheduling. The        scheduling functionality is located in the eNodeB, which has one        MAC entity per cell, for both uplink and downlink. The        hybrid-ARQ protocol part is present in both the transmitting and        receiving end of the MAC protocol. The MAC (507) offers services        to the RLC (505) in the form of logical channels (509).    -   Physical Layer (PHY, 511), handles coding/decoding,        modulation/demodulation, multi-antenna mapping, and other        typical physical layer functions. The physical layer (511)        offers services to the MAC layer (507) in the form of transport        channels (513).

FIG. 6 is a diagram for Scheduling-request transmission.

The scheduler needs knowledge about the amount of data awaitingtransmission from the terminals to assign the proper amount of uplinkresources. Obviously, there is no need to provide uplink resources to aterminal with no data to transmit as this would only result in theterminal performing padding to fill up the granted resources. Hence, asa minimum, the scheduler needs to know whether the terminal has data totransmit and should be given a grant. This is known as a schedulingrequest.

A scheduling request is a simple flag, raised by the terminal to requestuplink resources from the uplink scheduler. Since the terminalrequesting resources by definition has no PUSCH resource, the schedulingrequest is transmitted on the PUCCH. Each terminal can be assigned adedicated PUCCH scheduling request resource, occurring every nthsubframe. With a dedicated scheduling-request mechanism, there is noneed to provide the identity of the terminal requesting to be scheduledas the identity of the terminal is implicitly known from the resourcesupon which the request is transmitted.

When data with higher priority than already existing in the transmitbuffers arrives at the terminal and the terminal has no grant and hencecannot transmit the data, the terminal transmits a scheduling request atthe next possible instant, as illustrated in FIG. 15. Upon reception ofthe request, the scheduler can assign a grant to the terminal. If theterminal does not receive a scheduling grant until the next possiblescheduling-request instant, then the scheduling request is repeated.There is only a single scheduling-request bit, irrespective of thenumber of uplink component carriers the terminal is capable of. In thecase of carrier aggregation, the scheduling request is transmitted onthe primary component carrier, in line with the general principle ofPUCCH transmission on the primary component carrier only.

The use of a single bit for the scheduling request is motivated by thedesire to keep the uplink overhead small, as a multi-bit schedulingrequest would come at a higher cost. A consequence of the single-bitscheduling request is the limited knowledge at the eNodeB about thebuffer situation at the terminal when receiving such a request.Different scheduler implementations handle this differently. Onepossibility is to assign a small amount of resources to ensure that theterminal can exploit them efficiently without becoming power limited.Once the terminal has started to transmit on the UL-SCH, more detailedinformation about the buffer status and power headroom can be providedthrough the inband MAC control message, as discussed below. Knowledge ofthe service type may also be used—for example, in the case of voice theuplink resource to grant is preferably the size of a typicalvoice-over-IP package. The scheduler may also exploit, for example,path-loss measurements used for mobility and handover decisions toestimate the amount of resources the terminal may efficiently utilize.

An alternative to a dedicated scheduling-request mechanism would be acontention-based design. In such a design, multiple terminals share acommon resource and provide their identity as part of the request. Thisis similar to the design of the random access.

The number of bits transmitted from a terminal as part of a requestwould in this case be larger, with the correspondingly larger need forresources. In contrast, the resources are shared by multiple users.Basically, contention-based designs are suitable for a situation wherethere are a large number of terminals in the cell and the trafficintensity, and hence the scheduling intensity, is low. In situationswith higher intensities, the collision rate between different terminalssimultaneously requesting resources would be too high and lead to aninefficient design.

Although the scheduling-request design for LTE relies on dedicatedresources, a terminal that has not been allocated such resourcesobviously cannot transmit a scheduling request. Instead, terminalswithout scheduling-request resources configured rely on therandom-access mechanism. In principle, an LTE terminal can therefore beconfigured to rely on a contention-based mechanism if this isadvantageous in a specific deployment.

The Scheduling Request (SR) is used for requesting UL-SCH resources fornew transmission. When an SR is triggered, it shall be considered aspending until it is cancelled. All pending SR(s) shall be cancelled andsr-ProhibitTimer shall be stopped when a MAC PDU is assembled and thisPDU includes a BSR which contains buffer status up to (and including)the last event that triggered a BSR, or when the UL grant(s) canaccommodate all pending data available for transmission.

If an SR is triggered and there is no other SR pending, the UE may setthe SR_COUNTER to 0.

As long as one SR is pending, if no UL-SCH resources are available for atransmission in this TTI, the UE may initiate a Random Access procedureon a PCell and cancel all pending SRs if the UE has no valid PUCCHresource for SR configured in any TTI.

Else if the UE has a valid PUCCH resource for SR configured for this TTIand if this TTI is not part of a measurement gap and if sr-ProhibitTimeris not running, if SR_COUNTER<dsr-TransMax, the UE may incrementSR_COUNTER by 1, instruct the physical layer to signal the SR on PUCCH,and start the sr-ProhibitTimer.

If SR_COUNTER≥dsr-TransMax, the UE may notify RRC to release PUCCH/SRSfor all serving cells, clear any configured downlink assignments anduplink grants, and initiate a Random Access procedure on the PCell andcancel all pending SRs.

FIG. 7 is a diagram for describing a random access procedure.

(1) 1^(st) Message Transmission

First of all, a user equipment randomly selects a random access preamblefrom a set of random access preambles indicated by system information ora handover command, selects a PRACH (physical RACH) resource forcarrying the random access preamble, and then transmits the randomaccess preamble via the selected PRACH resource [S701].

(2) 2^(nd) Message Reception

After the user equipment has transmitted the random access preamble inthe step S701, the user equipment attempts a reception of its randomaccess response in a random access response receiving window indicatedby an eNode B through the system information or the handover command[S702]. In particular, the random access response information may betransmitted in format of MAC PDU. And, the MAC PDU may be carried onPDSCH (physical downlink shared channel). In order to receive theinformation carried on the PDSCH, the user equipment preferably monitorsPDCCH (physical downlink control channel). In particular, information ona user equipment necessary to receive the PDSCH, a frequency and timeinformation of a radio resource of the PDSCH, a transmission format ofthe PDSCH and the like may be preferably included in the PDCCH. Once theuser equipment succeeds in the reception of the PDCCH transmitted to theuser equipment, it may be able to appropriately receive a random accessresponse carried on the PDSCH in accordance with the informations of thePDCCH. And, a random access preamble identifier (ID) (e.g., RAPID(random access preamble identifier), a UL grant indicating a UL radioresource, a temporary cell identifier (temporary C-RNTI), timesynchronization correction value (timing advance command (TAC)) and thelike can be included in the random access response.

As mentioned in the foregoing description, the random access preambleidentifier is required for the random access response. Since randomaccess response information for at least one or more user equipments maybe included in one random access preamble, it may be necessary toindicate the UL grant, the temporary cell identifier and the TAC arevalid for which user equipment. In this step, assume that the userequipment selects a random access preamble identifier matching therandom access preamble selected by the user equipment in the step S702.Through this, the user equipment may be able to receive a UL grant, atemporary cell identifier 9temporary C-RNTI), time synchronizationcorrection value (timing advance command: TAC) and the like.

(3) 3^(rd) Message Transmission

If the user equipment receives the random access response valid for theuser equipment, it may process the informations included in the randomaccess response. In particular, the user equipment applies the TAC andsaves the temporary cell identifier. Moreover, the user equipment may beable to save data, which is to be transmitted in response to the validrandom access response, in a message-3 buffer.

Meanwhile, using the received UL grant, the user equipment transmitsdata (i.e., a 3rd message) to the eNode B [S703]. For an example, thedata may include the Buffer Status Report. In the contention basedrandom access procedure, an eNode B is unable to determine which userequipments perform the random access procedure. In order for resolve thecontention later, the eNode B needs to identify a user equipment.

As a method of including an identifier of a user equipment, two kinds ofmethods have been discussed. According to a 1st method, if a userequipment has a valid cell identifier already allocated by acorresponding cell prior to the random access procedure, the userequipment transmits its cell identifier via UL transmission signalcorresponding to the UL grant. On the contrary, if the user equipmentfails to receive the allocation of a valid cell identifier prior to therandom access procedure, the user equipment transmits its uniqueidentifier (e.g., S-TMSI, random ID (Random Id), etc.). In general, theunique identifier is longer than the cell identifier. If the userequipment transmits data corresponding to the UL grant, the userequipment initiates a contention resolution timer (hereinafterabbreviated CR timer).

(4) 4^(th) Message Reception

After the user equipment has transmitted the data including itsidentifier via the UL grant included in the random access response, theuser equipment waits for an instruction from the eNode B for thecontention resolution. In particular, the user equipment may attempt areception of PDCCH to receive a specific message [S704]. As a method ofreceiving the PDCCH, two kinds of methods have been discussed. Asmentioned in the foregoing description, if the 3rd message transmittedin response to the UL grant uses a cell identifier as its identifier,the user equipment attempts a reception of PDCCH using its cellidentifier. If the identifier is a unique identifier, the user equipmentmay be able to attempt a reception of PDCCH using a temporary cellidentifier included in the random access response. Thereafter, in theformer case, if the PDCCH is received via its cell identifier beforeexpiration of the contention resolution timer, the user equipmentdetermines that the random access procedure is normally performed andthen ends the random access procedure. In the latter case, if PDCCH isreceived via a temporary cell identifier before expiration of thecontention resolution timer, the user equipment checks data carried onPDSCH indicated by the PDCCH. If the unique identifier of the userequipment is included in a content of the data, the user equipmentdetermines that the random access procedure is normally performed andthen ends the random access procedure.

The Buffer Status Reporting (BSR) procedure is used to provide a servingeNB with information about the amount of data available for transmissionin the UL buffers of the UE. RRC may control BSR reporting byconfiguring the two timers periodicBSR-Timer and retxBSR-Timer and by,for each logical channel, optionally signaling Logical Channel Groupwhich allocates the logical channel to an LCG (Logical Channel Group).

For the Buffer Status reporting procedure, the UE may consider all radiobearers which are not suspended and may consider radio bearers which aresuspended. A Buffer Status Report (BSR) may be triggered if any of thefollowing events occur:

-   -   UL data, for a logical channel which belongs to a LCG, becomes        available for transmission in the RLC entity or in the PDCP        entity and either the data belongs to a logical channel with        higher priority than the priorities of the logical channels        which belong to any LCG and for which data is already available        for transmission, or there is no data available for transmission        for any of the logical channels which belong to a LCG, in which        case the BSR is referred below to as “Regular BSR”;    -   UL resources are allocated and number of padding bits is equal        to or larger than the size of the Buffer Status Report MAC        control element plus its subheader, in which case the BSR is        referred below to as “Padding BSR”;    -   retxBSR-Timer expires and the UE has data available for        transmission for any of the logical channels which belong to a        LCG, in which case the BSR is referred below to as “Regular        BSR”;    -   periodicBSR-Timer expires, in which case the BSR is referred        below to as “Periodic BSR”.

For Regular and Periodic BSR, if more than one LCG has data availablefor transmission in the TTI where the BSR is transmitted, the UE mayreport Long BSR. If else, the UE may report Short BSR.

If the Buffer Status reporting procedure determines that at least oneBSR has been triggered and not cancelled, if the UE has UL resourcesallocated for new transmission for this TTI, the UE may instruct theMultiplexing and Assembly procedure to generate the BSR MAC controlelement(s), start or restart periodicBSR-Timer except when all thegenerated BSRs are Truncated BSRs, and start or restart retxBSR-Timer.

Else if a Regular BSR has been triggered, if an uplink grant is notconfigured or the Regular BSR was not triggered due to data becomingavailable for transmission for a logical channel for which logicalchannel SR masking (logicalChannelSR-Mask) is setup by upper layers, aScheduling Request shall be triggered.

A MAC PDU may contain at most one MAC BSR control element, even whenmultiple events trigger a BSR by the time a BSR can be transmitted inwhich case the Regular BSR and the Periodic BSR shall have precedenceover the padding BSR.

The UE may restart retxBSR-Timer upon indication of a grant fortransmission of new data on any UL-SCH.

All triggered BSRs may be cancelled in case UL grants in this subframecan accommodate all pending data available for transmission but is notsufficient to additionally accommodate the BSR MAC control element plusits subheader. All triggered BSRs shall be cancelled when a BSR isincluded in a MAC PDU for transmission.

The UE shall transmit at most one Regular/Periodic BSR in a TTI. If theUE is requested to transmit multiple MAC PDUs in a TTI, it may include apadding BSR in any of the MAC PDUs which do not contain aRegular/Periodic BSR.

All BSRs transmitted in a TTI always reflect the buffer status after allMAC PDUs have been built for this TTI. Each LCG shall report at the mostone buffer status value per TTI and this value shall be reported in allBSRs reporting buffer status for this LCG.

In summary, the BSR is triggered in any of the following situation:

i) when data arrive for a logical channel which has higher priority thanthe logical channels whose buffers are not empty;

ii) when data become available for the UE's buffer, which is empty;

iii) when the retxBSR-Timer expires and there is still data in the UE'sbuffer;

iv) when a periodicBSR-Timer expires; or

v) when the remaining space in a MAC PDU can accommodate a BSR.

In LTE, the procedure for the UE to transmit infrequent UL packet to theeNB is as follows.

If the UE is in an RRC connected state and has valid PUCCH resourceavailable for transmitting the Scheduling Request, the UE may transmitthe Scheduling Request to the eNB through the PUCCH resource for theScheduling Request. On the other hand, if the UE is in an RRC Idle stateor no valid PUCCH resources are available for the Scheduling Request,the UE may initiate a Random Access procedure.

Thereafter, the UE may transmit the Buffer Status Report to the eNB andreceive the UL grant in response to Buffer Status Report from the eNB.After that, the UE may transmit the infrequent UL packets based on theUL grant. In any way, the infrequent UL packet (e.g., UL-SCH data or L2data) is transmitted only based on UL grant.

However, when performing such a procedure, it takes much time for the UEto transmit infrequent UL packets. In LTE New Radio (NR) technology for5G, it is important to ensure very short latency for uplink user planepackets, especially for infrequent small packets. Therefore, a mechanismto support short latency for the infrequent small packets is needed.

FIG. 8 is a flowchart illustrating data transmission according to anembodiment of the present invention.

Referring to FIG. 8, the UE may receive configuration informationincluding contention based channel configuration and trafficcharacteristic associated with the contention based channelconfiguration (S810). The traffic characteristic may be defined as apart of the contention based channel configuration. The contention basedchannel may be replaced with the term Fast UL Channel (FUCH).

As shown above, in the legacy system, the UE performs Scheduling Requesttransmission or Random Access procedure according to the state (i.e.,Idle mode or Connected mode) of the UE. However, the contention basedchannel can be used by the UEs in both the Idle mode and Connected mode.

The UE can configure multiple contention based channels depending on thecharacteristics of the traffic served by each contention based channel.The UE also configures PDCP/RLC/MAC for each contention based channelaccording to the configuration information. For this, the UE mayconfigure one PDCP, one RLC, and one MAC for the one contention basedchannel. In other word, all traffics may be transmitted by a contentionbased channel using the same PDCP/RLC/MAC. For an example, UE may notconfigure PDCP or RLC. Each packet transmitted on contention basedchannel may be handled independently, i.e. there is no relationshipbetween subsequent packets.

The configuration information including contention based channelconfiguration is received via a dedicated signaling or common/broadcastsignaling. As an example, contention based channel configuration isprovided by the eNB using system information. As an example, thecontention based channel configuration may include at least one of oneor more radio resources of the contention based channel resource,subframe information of the contention based channel resource, Layer 2configuration of the contention based channel resource; or securityinformation used for the contention based channel resource. At thistime, the contention based channel configuration may contain at leastone of following information for contention based channel.

-   -   Traffic characteristics including at least one of (i) Traffic        type that can be transmitted by contention based channel (e.g.        Voice, Streaming, Interactive, Background), (ii) a maximum        packet size that can be transmitted by the contention based        channel resource, (iii) a maximum delay that can be transmitted        by the contention based channel resource, (iv) a maximum error        ratio that can be transmitted by the contention based channel        resource, or (v) QoS Class Indicator (QCI) of the traffic that        can be transmitted by contention based channel.    -   contention based channel radio resource configuration (e.g.        time, frequency, subframe)    -   Layer 2 configuration, e.g. PDCP/RLC/MAC configuration. It is        possible that there is no PDCP or RLC defined for contention        based channel. In this case, PDCP or RLC configuration is        indicated as N/A. MAC configuration for contention based channel        can be simplified compared to prior art, i.e. no Logical Channel        Prioritization (no multiplexing), no SR/BSR/RACH, no MAC Control        Element.    -   Security information used for contention based channel    -   UE state that can use this contention based channel. At least        one of Idle/Connected/Suspend/Resume state can be indicated. For        example, this contention based channel can be used by both Idle        and Connected UEs, only Idle UEs, or only Connected UEs.

For another example, the information may contain more than onecontention based channel configuration. In addition, the informationcontaining contention based channel configuration may be broadcastperiodically, e.g., through system information.

As another example, the eNB may provide the contention based channelconfiguration to the UE by dedicated signaling. In this case, the UEprioritizes the contention based channel configuration received bydedicated signaling over the contention based channel configurationreceived by system information.

Subsequently, the UE may configure a contention based channel (e.g.,contention based channel resource) according to the contention basedchannel configuration (S820). For example, the contention based channelresource may be a time-frequency resource on which multiple UEs cantransmit UL packet, simultaneously. The contention based channelresource may be periodically configured on a set of subframes, e.g.,which is defined by a subframe period and a subframe offset.

After the configuration is set up, if UL data (e.g, UL-SCH data or L2data) to be transmitted occurs or becomes available, the UE may checkwhether the uplink data is suitable for the traffic characteristicassociated with the contention based channel configuration (S830).

If the UL data is suitable for the traffic characteristic associatedwith the contention based channel configuration, the UE may transmit theUL data using the contention based channel resource (S840) which doesnot require UL grant. As an example, multiple UEs can transmit UL packetusing a same contention based channel resource in a same subframe. Ifcontention happens, the eNB may not receive some or all of packetstransmitted from multiple UEs. The UE includes the identifier of the UEin the packets transmitted on contention based channel. For example, theUL data may be transmitted with an identifier of the UE on thecontention based channel resource. If the UE is in RRC connected mode,the identifier of the UE may be C-RNTI, and if the UE is in RRC idlemode, the identifier of the UE may be a unique ID for the UE such asIMSI (International Mobile Subscriber Identity) or GUTI (Globally UniqueTemporary Identifier).

As an example, there is no HARQ feedback for contention based channeltransmission. Instead, the HARQ feedback may be provided by RLC or NAS.For example, after UL data is transmitted through contention basedchannel, UE does not perform a procedure for receiving HARQ feedback forcontention based channel transmission, but performs a procedure forreceiving ARQ feedback, which is provided by RLC or NAS, for contentionbased channel transmission.

On the other hand, if the UL data is not suitable for the trafficcharacteristic associated with the contention based channelconfiguration, the UE doesn't use the contention based channel resourceto transmit the UL data. Instead, the UE may transmit the UL data basedon the legacy transmission (S850). For an example, if the UE isconnected and has a dedicated SR resource, the UE transmits the UL datausing a UL grant received due to scheduling request (SR) and bufferstatus report (BSR). For another example, if the UE is connected butdoesn't have a dedicated scheduling request (SR) resource or the UE isin an idle state, the UE transmits the UL data using a UL grant receiveddue to random-access channel (RACH) and buffer status report (BSR). Inthis case, the UE may perform a procedure for receiving HARQ feedbackfor UL data transmission. A detailed description thereof is describedwith reference to FIGS. 6 and 7, and a description of legacycommunication is omitted.

FIG. 9 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 9 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 9, the apparatus may comprise a DSP/microprocessor(110) and RF module (transceiver; 135). The DSP/microprocessor (110) iselectrically connected with the transceiver (135) and controls it. Theapparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 9 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 9 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. The processor (110) isconfigured to perform operations according to the embodiment of thepresent invention exemplarily described with reference to theaccompanying drawings. In particular, the detailed operations of theprocessor (110) can refer to the contents described with reference toFIGS. 1 to 8.

The embodiments of the present invention described herein below arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term ‘eNB’ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from essential characteristics of the presentinvention. The above embodiments are therefore to be construed in allaspects as illustrative and not restrictive. The scope of the inventionshould be determined by the appended claims, not by the abovedescription, and all changes coming within the meaning of the appendedclaims are intended to be embraced therein.

INDUSTRIAL APPLICABILITY

While the above-described method has been described centering on anexample applied to the 3GPP LTE system, the present invention isapplicable to a variety of wireless communication systems in addition tothe 3GPP LTE system.

1. A method for a user equipment (UE) operating in a wirelesscommunication system, the method comprising: receiving, from a basestation (BS), information including configuration of a channel for datatransmission, wherein the configuration includes a data volume thresholdinforming maximum volume of data available to be transmitted on thechannel; based on i) uplink (UL) data of the UE and ii) the data volumethreshold, determining whether to transmit the UL data on the channel;and based on determining that the UE transmits the UL data on thechannel, transmitting the UL data on the channel.
 2. The methodaccording to claim 1, wherein the configuration further includes aQuality of service Class Indicator (QCI) of traffic that can betransmitted by a resource of the channel.
 3. The method according toclaim 1, wherein the configuration further includes at least one of: atraffic type that can be transmitted by a resource of the channel; amaximum delay that can be transmitted by the resource of the channel;and a maximum error ratio that can be transmitted by the resource of thechannel.
 4. The method according to claim 1, wherein the informationincludes multiple configurations of channels for data transmission. 5.The method according to claim 1, wherein the resource of the channel isa time-frequency resource on which multiple UEs can transmit UL data,simultaneously.
 6. The method according to claim 1, wherein the UL datais transmitted with an identifier of the UE on the resource of thechannel.
 7. The method according to claim 1, wherein the information isreceived via a dedicated signaling or system information.
 8. A userequipment (UE) in a wireless communication system, the UE comprising: atleast one transceiver; at least one processor; and at least one computermemory operably connectable to the at least one processor and storinginstructions that, when executed, cause the at least one processor toperform operations comprising: receiving, from a base station (BS),information including configuration of a channel for data transmission,wherein the configuration includes a data volume threshold informingmaximum volume of data available to be transmitted on the channel; basedon i) uplink (UL) data of the UE and ii) the data volume threshold,determining whether to transmit the UL data on the channel; and based ondetermining that the UE transmits the UL data on the channel,transmitting the UL data on the channel.
 9. The UE according to claim 8,wherein the configuration further includes a Quality of service ClassIndicator (QCI) of traffic that can be transmitted by a resource of thechannel.
 10. The UE according to claim 8, wherein the configurationfurther includes at least one of: a traffic type that can be transmittedby a resource of the channel; a maximum delay that can be transmitted bythe resource of the channel; and a maximum error ratio that can betransmitted by the resource of the channel.
 11. The UE according toclaim 8, wherein the information includes multiple configurations ofchannels for data transmission.
 12. The UE according to claim 8, whereinthe resource of the channel is a time-frequency resource on whichmultiple UEs can transmit UL data, simultaneously.
 13. The UE accordingto claim 8, wherein the UL data is transmitted with an identifier of theUE on the resource of the channel.
 14. The UE according to claim 8,wherein the information is received via a dedicated signaling or systeminformation.